As is known conventional skis are suitably arched and have a downward facing convex surface whose camber is referred to as "rise", in order to give the ski sufficient grip, that is, to ensure that it slides evenly and continuously over the ground, without side-slipping or pendular oscillations, both on the straight and on relatively wide-radius curves.
If, in fact, a ski has a high "rise" and, simultaneously, a high degree of flexural rigidity, the reaction load, due to the ground on which it is pressed and "flattened" by the weight of the skier, has a distribution which is highly concentrated at the ends, with separate relative maximum loads spaced considerably far apart.
This distribution, in fact, permits greater incision of the edges at the ends and, therefore, ensures greater stability.
It is also known, moreover, that when curving with parallel skis, each ski, and especially the outside one, must be able to bend in the reverse direction, especially in the front area towards the shovel. In fact, since it is also placed "edgewise", or slanting towards the inside of the curve (as a result of the analagous centripetal displacement of the barycentre of the skier and, earlier still, as a result of the "angulation" that he assumes by bending his legs and the top half of his body sideways), its "reverse bending", together with the natural lateral concavity of its plan profile enables the inside edge provided with a metal strip, to assume a deformed attitude identical to the curve.
But, in order to enable the skier to carry out this manoeuver easily (especially at the initial stage, during the "reversing of the edge", the ski should, on the contrary, have a low "rise" and a very limited flexural rigidity. It should be made in such a way as to submit to the reaction of the ground with the load concentrated to a great extent at the center.
For the conventional ski therefore, the situation is intrinsically contradictory, as far as its elastic properties are concerned. And so, the general tendency is to seek a compromise solution by shifting slightly in one direction or the other according to use or to the user for whom the ski is presumably destined and, moreover, according to the most up-to-date trends, tending mainly towards flexibility with sufficient flexural deformation as to give rise to a rather uniform distribution of the reaction load but with a single peak close to the center of the ski.
In this respect, manufacturers have perfected relatively sophisticated techniques, with multicomposite sandwich structures, in order to develop elastic properties aimed at achieving solutions capable of encouraging such compromise, by resorting to skis having a very high degree of rigidity over quite a wide area around the center line while having a considerably high degree of flexibility at the ends, especially towards the shovel;
skis having a very high degree of torsional rigidity in relation to flexural rigidity, that is to say, skis having a high ratio between said rigidities, especially towards the shovel.
Both these properties in fact give the ski quite good stability, both on the straight and in wide-radius curves, with reasonably satisfactory resistance to side-slipping and progressive driving, while at the same time permitting a certain amount of ease of movement in "reversing the edge" when approaching each subsequent curve.
This structural tendency however involves complex and costly technologies (sandwiches with numerous differential layers, including two preferably fine metal layers reinforced by adjacent layers in fiber or plastic), and it is nevertheless a compromise solution with which it is not possible to radically overcome the contradiction mentioned previously, which remains an intrinsic and physiological characteristic of the conventional "single continuous" bar structure of the ski.
This invention constitutes the logical outcome of this analysis and aims to radically overcome the aforesaid contradiction by providing a new ski structure capable of automatically adapting to the load conditions and in which the distribution of the reaction load can vary with variations in the conditions of use of the ski itself.
A further scope of this invention is to provide a ski of the aforementioned type, which can be inexpensively mass-produced, while at the same time keeping very high standard of quality.